Ross’s Goose

OIE DE ROSS

Chen rossii (Cassin)

 

Uncommon migrant in the south; more common towards the west; locally common migrant and rare breeder in the far north.

 

This diminutive Snow Goose look-alike, with its short neck and stubby bill, is much less common in most of Manitoba than its larger relative. It can be found by diligently scanning large flocks of Snow Geese; typically, one or two Ross’s Geese are seen for every 1000 Snows, but larger numbers are sometimes seen in extreme northern and western Manitoba. A few individuals occur alone or with Canada Geese.

 

This species’ principal migration route between California and the Queen Maud Gulf region crosses eastern Alberta and western Saskatchewan. However, some Ross’s Geese breed among the mid-continent population of Snow Geese and migrate with Snow Goose flocks through Manitoba. The first Manitoba specimen on record was shot near Winnipeg on 20 September 1902.^1‑3 Observations by Hearne at Churchill in 1771 seem to refer to this species, indicating that it is not a newcomer to the province, at least as a migrant.⁴ Nevertheless, the wintering population on the Gulf Coast, much of which is thought to breed in the Hudson Bay region, increased markedly during the 1960s to over 1000 birds by 1970.⁵

 

Ross’s Geese are frequently observed with Snow Geese during spring and fall migration on the Hudson Bay coast, as well as in southern staging areas, and the migration chronology of the two species is essentially the same. Ross’s Geese are normally observed in southern Manitoba from mid-April to early May and from mid-September to early November; extreme dates are 10 March and 7 December.

 

In some years, thousands of Ross’s Geese occur between late August and mid-September near Button Bay and Dymond Lake, west of Churchill. Presumably they then cross northwestern Manitoba en route to California. There is also a spring record of 1000 Ross’s Geese flying north at Churchill on 6 June 1998. Flocks of hundreds of Ross’s Geese are occasionally seen in spring in southwestern Manitoba. In contrast, spring counts at Oak Hammock Marsh rarely exceed a dozen birds, and the highest fall counts were 77 on 17 September 1995 and 72 on 20 September 1997. Fall sightings in the Lac du Bonnet area of eastern Manitoba have increased in recent years, along with growing numbers of staging Snow Geese, but they do not exceed single-digit totals.

 

The first breeding record for Manitoba was in 1972, when a pair of Ross’s Geese nested among the Snow Geese at La Pérouse Bay, east of Churchill; three additional nesting Ross’s Geese were each paired with Snow Geese.⁶ None had been found in three previous field seasons, but the species was recorded in 14 of 17 subsequent seasons. Ross’s Geese have remained near 1% of the colony population, but the proportion appears to be increasing. Numbers caught in annual banding drives increased from 23 out of 3000 geese in 1987 to 100 out of 5413 in 1998.

 

Hybrid Ross’s × Snow Geese are fertile and all manner of intergrades between the two species occur, but they are not easily identified. Hatch and Shortt described a hybrid specimen shot at Oakville on 5 October 1935.⁷ Most mixed pairs consist of a male Ross’s and a female Snow or hybrid. Banding studies have shown that some female Ross’s Geese and hybrids that hatch in Manitoba return to the province to breed. The rare blue Ross’s Goose, thought by some to be a back-crossed hybrid with “Blue Goose” ancestry, has been recorded at least four times in the province.

 

¹ Thompson 1890; ² Atkinson 1904; ³ Seton 1908; ⁴ MacInnes & Cooch 1963; ⁵ Prevett & MacInnes 1972; ⁶ Ryder & Cooke 1973; ⁷ Hatch & Shortt 1976.

 

F. Cooke